1. Technical Field
This invention relates to wet/dry vacuum cleaner systems and, more particularly, to a safety interlock circuit for interrupting current to a motor located in a wand mounted accessory of the system.
2. Discussion
Wet/dry vacuum cleaner systems are used in a variety of cleaning applications to clean a variety of upholstered objects and surfaces. To better accomplish this task, vacuum units often employ a motorized beater brush attachment unit that connects to an accessory wand of such a vacuum cleaner system. The accessory wand is then connected to a handle assembly having a nozzle for receiving one end of the accessory wand, which in turn is connected to a vacuum hose leading to a main vacuum assembly of the system. The beater brush attachment aids in loosening dirt, threads, lint and other debris from carpets.
Since the beater brush attachment is an electrically driven device, it will typically include an insulated electrical cable with an electrical plug on one end that connects to an electrical receptacle mounted in the handle assembly, thereby allowing electrical power to be supplied through insulated electrical wires in the vacuum hose and the handle assembly to the beater brush attachment. Safety problems may exist, however, whenever the beater brush attachment is disconnected from the nozzle handle leaving an exposed "live" electrical receptacle, or when the insulated electrical cable is accidentally cut or broken. Should any water or other liquid cleaning agent come in contact with the receptacle or a broken wire of the electrical cable, or should an operator touch the receptacle opening or wire end, the operator could receive an electrical shock.
One alternative to avoiding this shock hazard is to have a continuous connection from the main vacuum assembly, through the flexible vacuum hose leading to the handle assembly, and to the beater brush attachment attached to the nozzle of the handle assembly. This "continuous connection" arrangement would prevent the possibility of electrical shock because the electrified hose, as well as the beater brush attachment, would be removed and replaced with a non-electrified vacuum hose whenever a different attachment accessory for the vacuum system is to be used. Therefore, no chance of electrical shock will be present since no electricity will be supplied through the alternate, non-electrified vacuum hose.
Although the above arrangement will remove the possibility of electrical shock when the beater brush attachment is removed from the handle assembly and extension wand, the obvious disadvantage is the need to substitute the electrified vacuum hose with a non-electrified hose whenever the beater brush attachment is disconnected in favor of a different attachment accessory. With the wide variety of upholstered surfaces that may be encountered in a single cleaning application and the wide ranging attachment accessories for specific cleaning situations, it is desirable to be able to switch between several attachment accessories quickly, easily and efficiently during a single cleaning task. Having to change vacuum hoses whenever the beater brush attachment is to be used or removed is an inconvenience for the operator and contributes to inefficiency in the use of the vacuum system.
It would therefore be desirable to have a simple, low-cost safety interlock circuit that would operate to automatically shut off electricity through the vacuum hose and to the handle assembly whenever the beater brush attachment is disconnected from the handle assembly. This would avoid the shock hazard that an otherwise "live" electrified hose presents, while allowing the quick, easy and efficient interchange of various nozzle attachment accessories without also having to change to a non-electrified vacuum hose whenever it is desired to use nozzle attachments other than the beater attachment.